Dredged sediment (DS) derived from dredging operations poses a potential threat to the ecological environment. Proper disposal and utilization of DS remain a challenge. In this study, magnesium oxychloride cement (MOC) was adopted as an eco-friendly carrier for effective recycling of DS. Multiscale characterizations were applied to MOC pastes incorporated with DS or calcined dredged sediment (CDS) to investigate the feasibility of combining MOC with DS. Despite the negative influence on mechanical properties induced by the dilution effect, DS/CDS ameliorated the water resistance of MOC pastes. Strength retention test revealed that the compressive strength retention rate of MOC pastes blended with 10-40% DS was positively correlated to DS content, and the modification effect of DS was better than that of CDS. X-ray Diffraction, Fourier Transform Infrared spectroscopy, Thermogravimetry -Differential Thermogravimetry, Mercury Intrusion Porosimetry and Scanning Electron Microscope with Energy Dispersive Spectrometer were conducted to further decipher the modification mechanism of DS/CDS on MOC system. The results revealed that the addition of DS increased the porosity of the modified MOC pastes, providing more channels for water intrusion. Interestingly, the improvement of water resistance of MOC paste was still enhanced with the increasing content of DS. Insoluble gel-like phases was speculated to widely exist on MOC substrate and acicular Phase 5 crystals, impeding the intrusion of water and thereby improving the stability of MOC pastes in water. All the results pointed to the formation of amorphous Mg-Al-Si-Cl-H gel that improved the water resistance of the modified MOC paste. The developed MOC paste presents a promising strategy to improve the water resistance of MOC products and alleviate the burden of DS on the environment. The work in this report is part of our recent published work.